Ammunition device

ABSTRACT

The invention relates to a device for reducing the rotational speed of an ammunition unit, for instance a submunition unit, and at the same time imparting to the ammunition unit a lateral speed. The device comprises a body (6) arranged to be swung out from the ammunition unit (1) and be released in a specific outswung position. The body preferably consists of a band which is wrapped about the outer peripheral surface of the ammunition unit. One end (7) of the band is fixed to the ammunition unit in such a way that the band is released in a specific outswung position.

BACKGROUND OF THE INVENTION

The present invention relates to a device for reducing the rotationalspeed of an ammunition unit and at the same time imparting a lateralspeed to the ammunition unit.

Even if the invention can be used for all types of ammunition units forwhich a reduced rotational speed is desired, such as pyrotechnicalammunition, shaped-charge ammunition or the like, in the following theinvention will be described in connection with submunitions, for examplesubmunition units which are released from an aeronautical body, forinstance a shell canister or the like, over a target area for searchingthis area in a helical pattern during the fall of the submunitiontowards the target area. Such submunitions are previously described inU.S. patent application Ser. No. 028,949.

In order to efficiently search a large target area it is necessary tolimit the speed of fall towards the ground. Also a controlled rotationalspeed is necessary. The rotational speed must be high enough to makesure that the maximal interscan distance during the searching phase isless than the width of the target.

In case the submunition unit has no original rotational speed it isnecessary to impart such a speed to the unit. In U.S. Pat. No. 4,356,770a submunition unit is disclosed which has no original rotational speedbut which is imparted such a speed by means of a breakable driving bandwhich is fastened to the launching tube by one of its ends and partiallysurrounds the submunition unit.

On the other hand the rotational speed should not be too high for adesired wobbling, precession or helical motion to be maintained. For usein a modern artillery shell, for which the rotational speed amounts tomore than 10,000 rpm, the rotational speed of the submunition device hasto be reduced after separation from the shell body.

Prior art brake rotation devices for achieving a sensing motion areoften of the parachute type, but devices using mechanical vanes are alsopreviously known. In U.S. patent application Ser. No. 028,949 thesubmunition unit has a specific aerodynamical design so that acontrolled rotational speed is obtained and the fall speed is limited.

In order to avoid interference between the searching areas of eachsubmunition unit, and also to prevent a detonating submunition unit fromdisturbing other submunition units, the submunition units should have aspecific distribution in the lateral direction. In some cases thelateral spread imparted to the submunition units due to thetranslational speed of the shell at the separation is enough. In othercases it is necessary to impart to the submunition unit a specificlateral movement. When the submunition units are released above thecentral part of a target area lateral movements in different directionsshould be imparted to the submunition units in order to cover as large atarget area as possible.

For submunition units of the parachute type it is previously known tocontrol the lateral speed to some extent by controlling the parachute.From DE-PS 33 23 685 it is previously known to control the lateral speedin order to increase the effect on a target area. By means of a motorthe guide ropes of the parachute are actuated so that the submunitionunit during its free trajectory moves in a desired direction. This is acomplex system, however, and a comparatively large space in the shellcanister is required which reduces the number of submunition unitscontained in the shell canister.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a device by means ofwhich the lateral speed is obtained in a simple way and which devicerequires a minimum of space. According to the present invention a bodyis attached to the ammunition unit and arranged to swing outwardly andbe released in a specific outswung position, preferably when formsoutswung position of 70°-90° with respect to the ammunition unit.

In a preferred embodiment the body consists of a band which is wrappedaround the outer peripheral surface of the ammunition unit.

In the following a preferred embodiment of the invention present will bedescribed more in detail in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematically the scanning movement of a submunitionunit,

FIG. 2 illustrates schematically the band during unwinding from theouter peripheral surface of the submunition unit.

FIG. 3 illustrates the band in its outswung position just before beingreleased forming an outswung angle α=70°-90°.

FIGS. 4 and 4a illustrates an ammunition unit and a band havingcoinciding and non-coinciding centers of gravity.

FIG. 5 illustrates three ammunition units with respective bands fastenedin different circular positions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1 illustrates a submunition unit 1 which has been separated from acanister in a carrier shell. The carrier shell, the canister and theseparation procedure are not described here in any detail as they do notform part of the present invention. For instance the shell may be of15.5 cm calibre discharged from a field artillery piece in aconventional way in a ballistic trajectory towards a target area withdiscrete targets in the form of armoured vehicles 2 and 3. Thesubmunition unit may be of the type described in U.S. application Ser.No. 028,949 and which scans the target area in a helical pattern 4. Thearrow 5 indicates the desired lateral movement of the submunition unit.

FIG. 2 illustrates the system submunition unit with its body in the formof a band 6 arranged to be swung outwardly. The band 6 could be wrappedone or more loops around the peripheral surface of the submunition unit.The free end 8 of the band starts unwinding as soon as the submunitionunit has been separated from the carrier shell. The other end 7 of theband is fixed to the submunition unit 1 so that the band 6 is releasedin an outswung position (FIG. 3). When the band is unwound the moment ofinertia and the center of rotation of the system are changed. Therotational speed of the band and submunition unit is reduced. When theband has been released from the submunition body the submunitioncontinues its own movement in the tangential direction, i.e. itsdirection in the rotating system at the moment of separation. Thetangential speed of the submunition unit in the rotating system becomesthe lateral speed after separation. The number of revolutions and thelateral speed of the submunition unit after separation depends on theoriginal rotational speed and ratio of masses of the band and thesubmunition unit.

With a suitable mass proportion between the submunitions unit and theband, which do not make the stresses in the band itself and itsfastening point too high, a lateral speed of approximately 10 m/s can beobtained if the rotational speed of the band prior to separation amountsto 10,000 rpm. The separation phase itself takes approximately 10 ms.The rotational speed of the submunition unit in this case has decreasedto approximately 1000 rpm.

As illustrated in FIG. 2, in this case the width of the band isapproximately the same as the width of the submunition unit. Preferablythe band is located in a recess 9 in the outer peripheral surface. Theband is made of a high steel quality with an appropriate thickness.

If the center of gravity of the band and of the submunition unitcoincide (FIG. 4) in the direction of the rotational axis beforeseparation the submunition unit will rotate about the same axis afterseparation. If the centers of gravity do not coincide (FIG. 4a), thesubmunition unit will rotate about another axis after separation. Thenthe submunition unit becomes a tumbling movement, the frequency of whichcan be controlled by means of the relative positions of the centers ofgravity 20 and 21 for the band and the submunition unit respectively.The center of gravity of the band relative to the submunition unit caneasily be changed by making the band smaller and changing its positionin the direction of the symmetrical axis or making the mass distributionof the band non homogenic in the direction of the symmetrical axis.

By arranging the fastening point of the bands in different angularpositions 22 in the canister each submunition unit obtains its ownlateral direction (FIG. 5).

Even if the body which is arranged to the swung out preferably is madein the form of a band as illustrated also other forms can be used.

Even if the invention now has been described substantially in connectionwith a submunition unit it should be understood that the invention isnot limited to that type of ammunition unit but can be used also forother types of such units in which a lateral movement is desired at thesame time as a reduction of the rotational speed is obtained.

We claim:
 1. In combination with an ammunition unit a device forreducing the rotational speed of said ammunition unit, and at the sametime imparting a lateral speed to said unit, said ammunition unitincluding a substantially cylindrical outer surface, said devicecomprising a single band wrapped around the outer peripheral surface ofsaid unit, said band being asymmetrically attached at one end to saidunit such as to swing outwardly and be released from the surface of saidunit when said band forms a predetermined outswung angle with respect tosaid ammunition unit, whereby imparting lateral speed to the ammunitionunit.
 2. A device according to claim 1, wherein said outswung angle isin a range of 70°-90°.
 3. A device according to claim 1, wherein thecenter of gravity of the ammunition unit and of the band coincide in thedirection of the rotational axis before separation, such that a stable,decreased rotation about the same rotational axis is imparted to theammunition unit after separation.
 4. A device according to claim 1,wherein the center of gravity of the ammunition unit and of the band aredisplaced with respect to each other in the direction of the rotationalaxis before separation in order to provide the ammunition unit with arotation about another axis.
 5. A device according to claim 1, whereinwhen discharging a number of ammunition unit, said units are spread indifferent lateral directions by means of different angular positions ofthe fastening points of the different bands.